1. Field of Invention
The present invention relates to a biaxially oriented polyester film. More specifically, the invention relates to a biaxially oriented polyester film suitable in use for wrapping films, capacitor films and magnetic tape base films, etc.
2. Description of the Prior Art
U.S. Pat. No. 3,884,870 discloses a biaxially oriented polyester film which includes an inert additive such as titanium oxide, silica or calcium carbonate to obtain good handleability and a good slipping property in the film.
However, such a conventional film does not satisfy recent severe requirements for processing the film, because the scratch resistance (the property preventing the surface of the film from being scratched) and the chipping resistance (the property preventing a substance of the film from coming off from the surface of the film) required for the film when the film is processed, for example, in a printing process to make a wrapping film or a magnetic layer application process and a calendering process to make a magnetic tape is not adequate and the demands on tapes have greatly increased associated with the increase in the speeds of these processes.